(1) Field of the Invention
This invention relates to butadiene-base polymers having an improved processability and a process for producing the same.
(2) Description of the Prior Art
From demands for running safety and low fuel consumption in the automobiles, there have been proposed butadiene-base polymers having a high content of vinyl bond in butadiene portion and containing a branched polymer as a rubber materials for use in tire tread having improved breaking strength, wet-skid resistance, hysteresis properties and the like as disclosed, for instance, in Japanese Patent laid open No. 57-55,912 and No. 57-87,407.
However, when these butadiene-base polymers are used alone, they have problems in processability because the mill processability during the extrusion of the kneaded mass with carbon black is poor and also the glossiness and smoothness of the extrudate are poor. Thus, the butadiene-base polymer of this type should be used as a blend with other rubber.